Vibration sensor

ABSTRACT

A single vibration sensor producing multistage outputs corresponding to various vibrational acceleration values is disclosed. This vibration sensor is the type in which vibrational acceleration causes a movable gravitation element to move, and the movement of the element exerts pressure on a plunger which actuates a switch mechanism and outputs a signal. A feature of this vibration sensor is the switch mechanism includes a number of discrete switch units each having a different operating sensitivity. The switch units have a number of movable members which are displaced by the plunger when the vibrational acceleration causes the movable gravitation element to move, and a number of fixed contacts corresponding to these movable members with which the movable contacts come in contact. The spatial relationship of the fixed contacts with respect to the movable members is a feature which determines the operational sensitivity.

FIELD OF THE INVENTION

This invention concerns a sensor for detecting earthquakes or vibration.

BACKGROUND OF THE INVENTION

In an existing vibration sensor, as can be seen in FIG. 17, there arethree forces which act on a sphere (movable gravitation element) 70: theforce F₁ of gravitational acceleration; the force F₂ of seismicacceleration; and the spring force F₃ of movable member 71. The movementof sphere 70 is determined by the ratio of each of forces F₁, F₂ and F₃in the direction of an incline.

When a given seismic acceleration G acts on the vibration sensor, thecomponent of force F₂ in the direction of the incline which is due toseismic acceleration G becomes larger than the component of force F₁ inthe direction of the incline which is due to the gravitationalacceleration which acts on sphere 70. Sphere 70 moves from rest 72 toconical surface 73 and pushes plunger 74 upward. Plunger 74 thenactuates projection 75, which in turn pushes movable member 71 upward atpressure point A and causes it to bend. Movable contact 76 on movablemember 71 comes in contact with fixed contact 77, which closes theswitch and detects the seismic acceleration G.

The prior art vibration sensor described above detects vibration onlywhen the force exceeds a given seismic acceleration G. If we wish toapply different processing according to the magnitude of the seismicacceleration, we have no choice but to employ a number of discretevibration sensors.

SUMMARY OF THE INVENTION

This invention was developed in consideration of the problem describedabove. An objective of the invention is to provide a vibration sensorhaving multistage outputs corresponding to various seismic accelerationvalues.

To achieve the above objective, a vibration sensor for sensing avibrational acceleration is disclosed. This vibration sensor includes amovable gravitation element which is movable by the vibrationalacceleration, a plunger detecting a movement of the movable gravitationelement and a switch mechanism actuated by the plunger. A feature ofthis vibration sensor is the switch mechanism includes a number ofswitch units each having a different operating sensitivity. An advantageof this is each switch unit outputs a signal when it detects thevibrational acceleration which corresponds to its own operatingsensitivity. As a result, a single vibration sensor producing multistageoutputs corresponding to various vibrational acceleration values isachieved.

Another feature of the invention is each of the switch units includes amovable member which is displaced by the movable gravitation element anda number of fixed contacts with which the movable member comes intocontact. An advantage of this feature is the movable member operates ina series of stages depending on the vibrational acceleration so that fora given vibration, the movable member comes in contact with whichever ofthe fixed contacts that corresponds to that particular vibrationalacceleration.

Another feature of the invention is each of the switch units includes anumber of movable members which are displaced by the plunger when thevibrational acceleration causes the movable gravitation element to move,and a number of fixed contacts corresponding to these movable memberswith which the movable members come in contact. The spatial relationshipof the fixed contacts with respect to the movable members determines theoperational sensitivity. An advantage of this feature is the movablemember corresponding to a given acceleration operates when thatacceleration is experienced, and it comes in contact with its pairedfixed contacts.

Another feature of the invention is the movable gravitation element ofthe vibration sensor may be a sphere or a pendulum.

Another feature of the invention is the vibration sensor includes meansfor adjusting the operating sensitivity of the sensor. An advantage ofthis feature is in addition to being able to use the sensor, theoperating sensitivity can be adjusted in producing multistage outputs.

Another feature of the invention is the adjusting means consists of agap adjusting means for adjusting a gap between the contact on themovable member and the fixed contact. An advantage of this feature ofthe invention is the gap between a contact on the movable member and thefixed contact can be adjusted by the gap adjusting means for thatpurpose. That is, in addition to being able to use the sensor, thesensitivity can be adjusted in producing multistage outputs.

Another feature of the invention is the switch units in the vibrationsensor are snap-action type switches. An advantage of the snap-actionswitches is they minimize any fluctuation in the operating sensitivity.

Yet another feature of the invention is the switch mechanism consists ofa number of switch units with different operating sensitivities. Withregard to this feature of the invention, a number of variables are usedto determine the operating sensitivities, such as vibrational force F₂,a component of force F₂ in the direction of the incline (F₂ '),gravitational acceleration force F₁, and a component of force F₁ in thedirection of the incline (F₁ '). The inclined surface onto which thesphere moves when F₂ ' becomes larger than F₁ ' consists of a number ofinclined surfaces with different angles of inclination which correspondto various operating sensitivities. An advantage of this feature is avibrational acceleration of a given magnitude causes the sphere to moveonto the inclined surface which corresponds to that magnitude ofacceleration, and this exerts pressure on the plunger to actuate one ofthe switch units. Thus, a single vibration sensor producing multistageoutputs corresponding to various vibrational accelerations is achieved.

The above features and advantages of the invention will be betterunderstood from the following detailed description taken intoconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross section of a vibration sensor which is thefirst ideal embodiment of this invention.

FIG. 2 is a cross section of the base and switch mechanism in the samevibration sensor.

FIG. 3 is a view of the sensor in FIG. 2 from point W.

FIG. 4 illustrates the principle underlying the operation of thevibration sensor. In particular, FIGS. 4(A)-4(D) are a vector analysisof forces F₁, F₂ and F₃, the force resulting from gravitationalacceleration, the force resulting from seismic acceleration and thespring force of the movable member.

FIG. 5 shows the relationship between the stroke of the plunger and theload in the same vibration sensor.

FIG. 6 is a vertical cross section of a vibration sensor which is thesecond ideal embodiment of this invention.

FIG. 7 is a plan view of the switch mechanism in the same vibrationsensor.

FIGS. 8(A) and 8(B) show how this vibration sensor works.

FIG. 9 is a vertical cross section of the vibration sensor which is thethird ideal embodiment of this invention.

FIG. 10 is a plan view of the switch mechanism in the same vibrationsensor.

FIG. 11 shows the relationship between the stroke of the plunger theload in this vibration sensor.

FIG. 12 is a cross section of the base and the switch mechanism of thevibration sensor which is the fourth embodiment of this invention.

FIG. 13 is the same base viewed from Y in FIG. 12.

FIG. 14 illustrates the plunger.

FIG. 15 shows a vibration sensor which is the fifth ideal embodiment ofthis invention.

FIG. 16 is a simplified view of a portion of the sensor mechanism in avibration sensor according to this invention.

FIG. 17 is a vertical cross section of a vibration sensor belonging tothe prior art.

DETAILED DESCRIPTION OF THE INVENTION

In this section we shall discuss several embodiments of this inventionwith reference to the drawings.

Embodiment 1

A vibration sensor which is the first ideal embodiment of this inventionis illustrated in FIGS. 1 through 5.

FIG. 1 is a vertical cross section of a vibration sensor which is thefirst ideal embodiment of this invention. FIG. 2 is a cross section ofthe base and switch mechanism. FIG. 3 is a view of the sensor in FIG. 2from point W. FIG. 4 illustrates the principle underlying the operationof the sensor. In particular, FIGS. 4(A)-4(D) illustrate a vectoranalysis of forces F₁, F₂ and F₃, the force resulting from gravitationalacceleration, the force resulting from seismic acceleration and thespring force of the movable member. FIG. 5 shows the relationshipbetween the stroke of the plunger and the load.

The vibration sensor of the first ideal embodiment of this invention isa two-stage output sensor. This sensor consists primarily of cylindricalexternal case 1, cap 10, damper 8 and vibration sensor mechanism B. Cap10 covers the external case 1 and, together, they constitute package A.Damper 8 is attached to the interior surface of cap 10 and vibrationsensor mechanism B is enclosed in package A.

The top of the external case 1 is left open. There is an aperture 2 onits bottom surface la. On the interior periphery of external case 1 aretwo external common terminals 3, which run through bottom surface 1a ofexternal case 1 and protrude to the exterior. Two external fixingterminals (not pictured) are mounted on the external periphery ofexternal case 1.

The vibration sensor mechanism B is surrounded by internal case 9.Conical surface 12, with a slope of angle α, (see, for example, FIG.4(A)) is formed on the lower surface 11 of internal case 9. In thecenter of conical surface 12 is rest 13, on which is seated a sphere(movable gravitation element) 21.

Guide 14 is affixed to the upper end of internal case 9. An annulargroove 15 which is open on top is formed on the inner periphery of guide14. The annular pendant portion 17 of the external periphery of plunger16 fits into groove 15 of guide 14 in such a way that it can slide upand down. On the underside of plunger 16 is sphere receptor 18; on theupper surface of the plunger is projection 19, which actuates thesensor.

Sphere 21, which is the movable object, is enclosed within the internalcase 9. It is seated on rest 13, with receptor 18 of plunger 16 incontact with its upper surface.

Base 22 is attached to the guide 14. As can be seen in FIGS. 1 through3, base 22 has a wall 23 which runs all along its periphery. This wall23 has three gaps, 23a, 23b and 23c. In the center of the undersurface22a of base 22 is semicircular stop 24. Plate-like internal commonterminal 25 is fixed on one side of the undersurface. First and secondinternal fixed terminals 26 and 27 are arranged in parallel on theundersurface of the base on the side opposite common terminal 25. Fixedcontact 26A projects from first fixed terminal 26, and fixed contact 27Afrom second fixed terminal 27.

The base 28a of movable member 28 is fixed to the internal commonterminal 25. In movable member 28, card-shaped movable contact element29 is fixed to the front portions of two narrow strips 28b, both ofwhich are fixed to base 28a. Pressure point A and movable contact 30 areon the end of movable contact element 29. The center of movable contactelement 29 serves as movable contact 31. Movable contact element 29 sitsatop internal fixed terminals 26 and 27 and lies across both of them.

First switch unit S₁ comprises movable contact 30 on movable member 28and first fixed contact 26A on internal fixed terminal 26. Second switchunit S₂ comprises movable contact 31 on movable member 28 and secondfixed contact 27A on internal fixed terminal 27. Together, first andsecond switch units S₁ and S₂ constitute switch mechanism S.

Winding site 25b on the base of the common terminal 25 projects out tothe exterior through gap 23a. Winding site 26b on the base of internalfixed terminal 26 projects out to the exterior through gap 23b. Windingsite 27b on the base of internal fixed terminal 27 projects out to theexterior through gap 23c.

When base 22 is fixed to the top of guide 14, projection 19 on plunger16 is in contact with pressure point A on movable member 28, as can beseen in FIG. 1.

Legs 32A engage in holes 22c on upper surface 22b of the base 22.Gate-shaped suspending component 32 is suspended from the base.Crosspiece 33 is inserted into component 32. Fulcrum 8 is fixed to thecenter of crosspiece 33. It is mounted to the lower surface ofhorizontal portion leg 32A of component 32 in such a way that it canswing. Together, these components constitute suspended mechanism R.

When a vibration sensor mechanism B configured as described above isinserted in external case 1, the ends of crosspiece 33 are supported byledges (not pictured) on the upper edge of the case. When in this statethe cap 10 is fixed to the top of external case 1, damper 8 on the innersurface of cap 10 is placed in contact with suspending component 32.Winding site 27B on internal fixed terminal 27 is fixed by a lead wireto its external fixed terminal. Winding site 25A on internal commonterminal 25 is fixed by a lead wire to external common terminal 3.

We shall next discuss the operation of a vibration sensor configured asdescribed above.

As can be seen in FIG. 4(A), sphere 21 is acted upon by three forces:F₁, the gravitational acceleration force; F₂, the seismic (orvibrational) acceleration force; and F₃, the spring force of movablemember 28. Which way sphere 21 will move is determined by theproportional weight of three components F₁ ', F₂ ' and F₃ '. These arethe components of the three forces in the direction of the incline.

Until movable contact 30 on movable member 28 touches fixed contact 26Aon internal fixed contact terminal 26 (i.e., until switch unit S₁closes), spring load F₃ may be considered infinitely small. Themagnitude of seismic acceleration G which will cause switch unit S₁ togo on is determined by the angle α of the incline, which is the slope ofconical surface 12. When switch unit S₁ closes, the spring in movablemember becomes shorter, so spring load F₃ increases. The load whenmovable contact 31 on movable member 28 comes in contact with fixedcontact 27A on internal fixed terminal 27 (i.e., when switch unit S₂closes) is determined by spring load F₃ (i.e., by the contact gap).

When a seismic acceleration G₁ acts on the vibration sensor and theincline component F₂ ' of the force F₂ resulting from this accelerationbecomes larger than the incline component F₁ ' of the force F₁ due togravitational acceleration, sphere 21 will be dislodged from rest 13 andmoves onto conical surface 12. The sphere will push upward againstplunger 16, and projection 19 on the plunger will press upward againstmovable member 28 at pressure point A, causing member 28 to bend.Movable contact 30 on movable member 28 will come in contact with fixedcontact 26A on internal fixed terminal 26, and switch unit S₁ willclose, detecting the seismic acceleration G₁ experienced at that moment.

When a seismic acceleration G₂ becomes larger than the seismicacceleration G₁ acts on the vibration sensor and the incline componentF₂ ' of the force F₂ resulting from this acceleration becomes largerthan the incline component F₁ ' of the force F₁ due to gravitationalacceleration, sphere 21 will again be dislodged from rest 13 and movesonto conical surface 12. The sphere will again push upward againstplunger 16, and projection 19 on the plunger will press upward againstmovable member 28 at pressure point A, causing member 28 to bend.Movable contact 30 on movable member 28 will come in contact with fixedcontact 26A on internal fixed terminal 26, and movable member 28 willbend. Movable contact 31 on movable member 28 will come in contact withfixed contact 27A on internal fixed terminal 27, and switch unit S₂ willclose, detecting the seismic acceleration G₂ experienced at that moment.

The relationship between the stroke of plunger 16 and spring load F₃ atthis time is shown in FIG. 5. Switch unit S₁ will close at a spring loadF₃ of 0.2 g; and switch unit S₂ will close at 6 g.

Embodiment 2

The vibration sensor which is the second embodiment of this invention ispictured in FIGS. 6 through 8.

FIG. 6 is a vertical cross section of a vibration sensor which is thesecond ideal embodiment of this invention. FIG. 7 is a plan view of theswitch mechanism in the same vibration sensor. FIGS. 8 (1) and (2) showhow this vibration sensor works.

In the vibration sensor of the second ideal embodiment of thisinvention, both ends of movable member 28 are supported, and a movablemember providing the movable contacts are supported on one side only. Inaddition, the heights of fixed contacts 26A and 27A on internal fixedterminals 26 and 27 are adjustable.

Conical surface 12 on the bottom 11 of internal case 9 in vibrationsensor mechanism B of this vibration sensor has an incline of angle a.In the center of conical surface 12 is rest 13-1, which consists of adepression on which sphere 21 is seated. Plate-shaped internal commonterminal 25 is fixed to one side of the undersurface 22a of base 22. Twogrooves, 36 and 37, straddle the center of the base to its right andleft; the terminals are inlaid in these grooves. Internal fixed terminal26 is inlaid in groove 36; internal fixed terminal 27 is inlaid ingroove 37. Terminals 26 and 27 are run parallel to each other.

Extremity 26a of internal fixed terminal 26 is fixed to undersurface22a. Screw 34, the gap adjusting means to adjust the gap and therebychange the sensitivity of the sensor, is screwed into base 22. The endof screw 34 is in contact with the free end 26b of internal fixedterminal 26. Extremity 27a of internal fixed terminal 27 is also fixedto undersurface 22a. Screw 35, the second gap adjusting means to adjustthe gap and thereby change the sensitivity of the sensor, is screwedinto base 22. The end of screw 35 is in contact with the free end 27b ofinternal fixed terminal 27. Fixed contact 26A projects from internalfixed terminal 26; fixed contact 27A projects from internal fixedterminal 27.

One end (the base portion) 28a, of movable member 28, is fixed to theinternal common terminal 25. The other end, 28c, is held betweenpressure ridge 39 on base 22 and the top edge of guide 14.

In movable member 28, card-shaped movable contact element 29 is fixed tothe front portions of two narrow strips 28b, both of which are fixed tobase 28a. Pressure point A and first and second movable contacts 30 and31 are on movable contact element 29. Movable contact element 29 sitsatop internal fixed terminals 26 and 27 and lies across both of them.

First switch unit S₁ comprises movable contact 30 on movable member 28and fixed contact 26A on first internal fixed terminal 26. Second switchunit S₂ comprises movable contact 31 on movable member 28 and fixedcontact 27A on second internal fixed terminal 27. Together, first andsecond switch units S₁ and S₂ constitute switch mechanism S.

Sphere 21 is enclosed within the internal case 9. It is seated on rest13-1, with receptor 18 of plunger 16 in contact with its upper surface.When base 22 is fixed to the top of guide 14, projection 19 on plunger16 is in contact with pressure point A on movable member 28. Otheraspects of this sensor which are identical to corresponding aspects ofthe first embodiment will not be discussed for brevity reason.

In this case, the forces acting on sphere 21 are F₁, the gravitationalacceleration force; F₂, the seismic acceleration force; and F₃, thespring force of movable member 28. Which way sphere 21 will move isdetermined by the proportional weight of three components, F₁ ', F₂ 'and F₃ '. These are the components of the three forces in the directionof the incline. (See FIG. 4.)

When a seismic acceleration G₁ acts on the vibration sensor and theincline component F₂ ' of the force F₂ resulting from this accelerationbecomes larger than the incline component F₁ ' of the force F₁ due togravitational acceleration, sphere 21 will be dislodged from rest 13 asin FIG. 8(A) and moves onto conical surface 13-1. The sphere will pushupward against plunger 16, and projection 19 on the plunger will pressupward against movable member 28 at pressure point A, causing member 28to bend. Movable contact 30 on movable member 28 will come in contactwith fixed contact 26A on first internal fixed terminal 26, and firstswitch unit S₁ will close, detecting the seismic acceleration G₁experienced at that moment.

When a seismic acceleration G₂ becomes larger than the seismicacceleration G₁, acts on the vibration sensor and the incline componentF₂ ' of the force F₂ resulting from this acceleration becomes largerthan the incline component F₁ ' of the force F₁ due to gravitationalacceleration, sphere 21 will again be dislodged from rest 13 and moveonto conical surface 13-1, as shown in FIG. 8(B). The sphere will againpush upward against plunger 16, and projection 19 on the plunger willpress upward against movable member 28 at pressure point A, causingmember 28 to bend. Movable contact 30 on movable member 28 will come incontact with fixed contact 26A on first internal fixed terminal 26, andmovable member 28 will bend. Movable contact 31 on movable member 28will, then, come in contact with fixed contact 27A on second internalfixed terminal 27, and second switch unit S₂ will close, detecting theseismic acceleration G₂ experienced at that moment.

To adjust the distance (i.e., the gap) between fixed contact 26A onfirst internal fixed terminal 26 and movable member 28 (movable contact30), the user turns screw 34 to bend or straighten first internal fixedterminal 26. To adjust the distance (or gap) between fixed contact 27Aon second internal fixed terminal 27 and movable member 28 (movablecontact 31), the user turns screw 35 to bend or straighten secondinternal fixed terminal 27.

Embodiment 3

The vibration sensor which is the third ideal embodiment of thisinvention is shown in FIGS. 9 through 11.

FIG. 9 is a vertical cross section of the vibration sensor of the thirdideal embodiment of this invention. FIG. 10 is a plan view of the switchmechanism in the same vibration sensor.

The third embodiment of the vibration sensor of this invention has threeoutput stages. Conical surface 12 on the bottom 11 of internal case 9 invibration sensor mechanism B of this vibration sensor has an incline ofangle α. In the center of conical surface 12 is rest 13-1, whichconsists of a depression on which sphere 21 is seated. Plate-shapedinternal common terminal 25 is fixed to one side of the undersurface 22aof base 22. Internal fixed terminals 26, 27 and 40 are fixed to baseportions 26a, 27a and 40a, respectively, on the undersurface of base 22.

The free ends of internal fixed terminals 26, 27 and 40 serve as springelements 26c, 27c and 40c. Spring elements 26c and 40c of terminals 26and 40 are card-shaped, and fixed contacts 26A and 40A are on their baseends. Spring element 27c of internal fixed terminal 27 is bent so thatit is V-shaped . Fixed contact 27A is at the intersection of the twoarms o f the V-shaped fixed terminal.

Three screws, 41, 42 and 43, are screwed into base 22 to allow the gapto be adjusted. These screws serve as the adjusting means to adjust thesensitivity of the sensor. The end of screw 41 is in contact with thefree end of spring element 26c of internal fixed terminal 26. The end ofscrew 42 is in contact with the free end of spring element 27c ofinternal fixed terminal 27. The end of screw 43 is in contact with thefree end of spring, element 40c of internal fixed terminal 40.

Movable member 44 consists of three units, 44-1, 44-2 and 44-3, onmounting base 45. Units 44-1, 44-2 and 44-3 are fixed to movable contactunit 46 at the front ends of two wirelike extensions 44b, which arefixed to mounting base 45. The front end of movable contact unit 46serves as pressure point A.

Movable member 44 is fixed to the internal common terminal 25 atmounting base 45. Unit 44-1 is placed over spring element 26c ofinternal fixed terminal 26; unit 44-2 is placed over spring element 27cof internal fixed terminal 27; and unit 44-3 is placed over springelement 40c of internal fixed terminal 40.

Projections 19-1, 19-2 and 19-3 on plunger 16 correspond to units 44-1,44-2 and 44-3, respectively.

Sphere 21 is inside the internal case 9. It is seated on rest 13-1, andreceptor 18 on plunger 16 is in contact with its upper surface. Base 22is fixed to the top of guide 14. Projections 19-1, 19-2 and 19-3 onplunger 16 are in contact with pressure points A of units 44-1, 44-2 and44-3. Other aspects of the configuration of the sensor that areidentical to corresponding aspects of the first embodiment will not bediscussed for brevity reason.

In this case, the forces acting on sphere 21 are F₁, the gravitationalacceleration force; F₂, the seismic acceleration force; and F₃, thespring force of movable unit 44-1 (or 44-2, or 44-3). Which way sphere21 will move is determined by the proportional weight of threecomponents, F₁ ', F₂ ' and F₃ '. These are the components of the threeforces in the direction of the incline. (See FIG. 4.)

When a seismic acceleration G₁ acts on the vibration sensor and theincline component F₂ ' of the force F₂ resulting from this accelerationbecomes larger than the incline component F₁ ' of the force F₁ due togravitational acceleration, sphere 21 will be dislodged from rest 13-1and moves onto conical surface 12. The sphere will push upward againstplunger 16, and projection 19-1 on the plunger will press upward againstmovable unit 44-1 at pressure point A, causing unit 44-1 to bend.Movable contact 46-1 on movable contact element 46 will come in contactwith fixed contact 26A on internal fixed terminal 26, and switch unit S₁Will close, detecting the seismic acceleration G₁ experienced at thatmoment.

When a seismic acceleration G₂ becomes larger than the seismicacceleration G₁ acts on the vibration sensor and the incline componentF₂ ' of the force F₂ resulting from this acceleration becomes largerthan the incline component F₁ ' of the force F₁ due to gravitationalacceleration, sphere 21 will again be dislodged from rest 13-1 and movesonto conical surface 12. The sphere will again push upward againstplunger 16, and projection 19-2 on the plunger will press upward againstmovable unit 44-2 at pressure point A, causing unit 44-2 to bend.Movable contact 46-2 on movable unit 44-2 will come in contact withfixed contact 27A on internal fixed terminal 27, and switch unit S₂ willclose, detecting the seismic acceleration G₂ experienced at that moment.

When a seismic acceleration G3 becomes larger than the seismicacceleration G₂ acts on the vibration sensor and the incline componentF₂ ' of the force F₂ resulting from this acceleration becomes largerthan the incline component F₁ ' of the force F₁ due to gravitationalacceleration, sphere 21 will again be dislodged from rest 13-1 and movesonto conical surface 12. The sphere will again push upward againstplunger 16, and projection 19-3 on the plunger will press upward againstmovable unit 44-3 at pressure point A, causing unit 44-3 to bend.Movable contact 46-3 on movable unit 44-3 will come in contact withfixed contact 40A on internal fixed terminal 40, and switch unit S₃ willclose, detecting the seismic acceleration G₃ experienced at that moment.

The relationship which obtains at this time between the stroke ofplunger 16 and spring load F₃ is shown in FIG. 11. Switch unit S₁ willclose at a spring load F₃ of 0.2 g; switch unit S₂ will close at a loadof 8 g; and switch unit S₃ will close at a load of 15 g.

Embodiment 4

A vibration sensor which is the fourth ideal embodiment of thisinvention is pictured in FIGS. 12 through 14.

FIG. 12 is a cross section of the base and the switch mechanism of thevibration sensor which is the fourth embodiment of this invention. FIG.13 is the same base viewed from Y in FIG. 12.

This vibration sensor of the fourth embodiment is similar to the thirdembodiment described above, except that a snap-action switch is used asswitch mechanism S. Since all other aspects of its configuration areidentical to those of the third embodiment, we shall not discuss themfurther at this point.

Snap-action switch mechanism S has three movable units, 44-1, 44-2 and44-3, on base 45 of movable element 44. These movable units are fixed tomovable contact 46 at the front ends of two wirelike extensions 44b,which are fixed to mounting base 45. Spring 47 is fixed to the rear endof movable contact 46.

Movable member 44 is fixed to the internal common terminal 25 atmounting base 45. Unit 44-1 is placed over spring element 26c ofinternal fixed terminal 26; unit 44-2 is placed over spring element 27cof internal fixed terminal 27; and unit 44-3 is placed over springelement 40c of internal fixed terminal 40. The free ends of springs 47of units 44-1, 44-2 and 44-3 are anchored in groove 48 on internalcommon terminal 25.

Projections 19-1, 19-2 and 19-3 on plunger 16, which can be seen in FIG.14, correspond to units 44-1, 44-2 and 44-3, respectively. Theseprojections straddle the springs 47 of the three units and are incontact with the pressure points A of the two long extensions 44b.

In this case, the forces acting on sphere 21 are F₁, the gravitationalacceleration force; F₂, the seismic acceleration force; and F₃, thespring force of movable unit 44-1 (or 44-2, or 44-3). Which way sphere21 will move is determined by F₁, F₂ and F₃ and by the proportionalweight of three components F₁ ', F₂ ' and F₃ '. These are the componentsof the three forces in the direction of the incline. (See FIG. 4.)

When a seismic acceleration G₁ acts on the vibration sensor and theincline component F₂ ' of the force F₂ resulting from this accelerationbecomes larger than the incline component F₁ ' of the force F₁ due togravitational acceleration, sphere 21 will be dislodged from rest 13-1and moves onto conical surface 12. The sphere will push upward againstplunger 16, and projection 19-1 on the plunger will press upward againstmovable unit 44-1 at pressure point A, causing unit 44-1 to bend.Movable contact 46-1 on movable unit 44-1 will come in contact withfixed contact 26A on internal fixed terminal 26, and switch unit S₁ willclose, detecting the seismic acceleration G₁ experienced at that moment.

When a seismic acceleration G₂ becomes larger than the seismicacceleration G₁ acts on the vibration sensor and the incline componentF₂ ' of the force F₂ resulting from this acceleration becomes largerthan the incline component F₁ ' of the force F₁ due to gravitationalacceleration, sphere 21 will again be dislodged from rest 13-1 and movesonto conical surface 12. The sphere will again push upward againstplunger 16, and projection 19-2 on the plunger will press upward againstmovable unit 44-2 at pressure point A, causing unit 44-2 to bend.Movable contact 46-2 on movable unit 44-2 will come in contact withfixed contact 27A on internal fixed terminal 27, and switch unit S₂ willclose, detecting the seismic acceleration G₂ experienced at that moment.

When a seismic acceleration G₃ becomes larger than the seismicacceleration G₂ acts on the vibration sensor and the incline componentF₂ ' of the force F₂ resulting from this acceleration becomes largerthan the incline component F₁ ' of the force F₁ due to gravitationalacceleration, sphere 21 will again be dislodged from rest 13-1 and movesonto conical surface 12. The sphere will again push upward againstplunger 16, and projection 19-3 on the plunger will press upward againstmovable unit 44-3 at pressure point A, causing unit 44-3 to bend.Movable contact 46-3 on movable unit 44-3 will come in contact withfixed contact 40A on internal fixed terminal 40, and switch unit S₃ willclose, detecting the seismic acceleration G₃ experienced at that moment.

This vibration sensor could detect three stages of vibration, forexample, vibration of magnitudes 5, 6 and 7. A vibration of magnitude 5would cause switch unit S₁ to close and the output of that switch to bedetected; a vibration of magnitude 6 would cause switch unit S₂ to closeand the output of that switch to be detected; and a vibration ofmagnitude 7 would cause switch unit S₃ to close and the output of thatswitch to be detected.

If this vibration sensor is installed in a gas meter (not pictured), thegas supply can be cut off when a vibration of magnitude 5 trips switchunit S₁, indicating that a gas leak has been detected. A vibration ofmagnitude 6 would trip switch unit S₂, and the gas supply would be cutoff but could be restored manually. A vibration of magnitude 7 wouldtrip switch unit S₃, and the gas supply would be cut off in such a waythat it could not be restored.

Embodiment 5

A vibration sensor which is the fifth ideal embodiment of this inventionis shown in FIG. 15.

In the vibration sensor of the fifth embodiment of this invention, apendulum is employed in place of sphere 21. This sensor primarilyconsists of cylindrical external case 50; cap 51, which covers case 50and with it constitutes package A; damper 52, which is attached to theinner surface of cap 51; and sensor mechanism B, which is housed inpackage A.

The vibration sensor mechanism B consists of suspended member 53; base54; switch mechanism S, which is supported by base 54; guide 55; andpendulum 56. Suspended member 53 is mounted on the upper surface 54b ofbase 54. Member 53 is supported in package A by suspension mechanism Rjust as is the corresponding component in the first embodiment. Switchmechanism S is fixed to undersurface 54a of base 54 in the same way asthe corresponding component is fixed in the second embodiment.

Guide 55 is fixed to the lower portion of base 54. On the upper surfaceof guide 55 are depression 58; aperture 59, which is in the center ofdepression 58; and stage 60, which is formed on the upper end ofaperture 59. Rod 61 of pendulum 56 has a hemispherical surface 62 on itsupper end. Plate 63 is fixed to the top of rod 61. Plunger 64 consistsof a small projection in the center of plate 63.

Rod 61 goes through aperture 59. Hemispherical surface 62 is in contactwith stage 60, and plate 63 is in contact with the surface of depression58. Pendulum 56 is set in guide 55.

When a seismic acceleration G₁ acts on the vibration sensor and thehorizontal component F₂ " of the force F₂₁ resulting from thisacceleration becomes larger than the horizontal component F₁ " of theforce F₁ due to gravitational acceleration, the pendulum 56 will swingat hemispherical surface 61 and plate 63 will rise up on its unilateralfulcrum, pushing upward against plunger 64. Projection 19 on the plungerwill press upward against movable member 28 at pressure point A, causingmember 28 to bend. Movable contact 30 on movable member 28 will come incontact with fixed contact 26A on internal fixed terminal 26, and switchunit S₁ will close, detecting the seismic acceleration G₁ experienced atthat moment. (See FIGS. 6 through 8.)

When a seismic acceleration G₂ becomes larger than the G₁ acts on thevibration sensor and the horizontal component F₂ " of the force F₂₁resulting from this acceleration becomes larger than the horizontalcomponent F₁ " of the force F₁ due to gravitational acceleration, thependulum 56 will again swing at hemispherical surface 61 and plate 63will rise up on its unilateral fulcrum, pushing upward against plunger64. Projection 19 on the plunger will press upward against movablemember 28 at pressure point A, causing member 28 to bend. Movablecontact 30 on movable member 28 will come in contact with fixed contact27A on internal fixed terminal 27, and switch unit S₂ will close,detecting the seismic acceleration G₂ experienced at that moment. (SeeFIGS. 6 through 8.)

A vibration sensor which employs a pendulum may be converted from atwo-stage to a three-stage output sensor by replacing the two-stageswitch mechanism S with the three-stage switch mechanism S shown in thethird and fourth embodiments.

In the sensor mechanism B described above, the conical surface 12 whichis formed on the lower surface 11 of internal case 9 has an incline α,and the center of this surface serves as rest 13, the stage on whichsphere 21 is seated. It would also be possible to use the design shownin FIG. 16, in which the conical surface consists of concentric arcs,each with an incline surface. The surface would then comprise conicalsurfaces 12-1, 12-2 and 12-3. Incline α₂ of conical surface 12-2 islarger than incline α₁, of surface 12-1; and incline α₃ of surface 12-3is larger than incline α₂. Each surface should have an incline whichcorresponds to the actuating vibration which causes sphere 21 to moveonto that incline (conical surface 12-1, 12-2 or 12-3).

Thus an earthquake of a given magnitude will cause sphere 21 to moveonto the incline which corresponds to that magnitude and through plunger16 actuate switch unit S₁ or S₂. A single vibration sensor can producemultistage output corresponding to the seismic (or vibrational)acceleration.

In embodiments 1 through 5 discussed above, the switch mechanism S isplaced over sphere 21; the switch mechanism S, however, could easily beplaced under the sphere.

As mentioned above, according to the vibration sensor disclosed in claim1, each switch unit outputs a signal when it detects a vibrationalacceleration which corresponds to its own operational sensitivity. Thusa single vibration sensor can produce multistage outputs correspondingto various vibrational acceleration values.

According to the vibration sensor disclosed in claim 2, the movablemember operates in a series of stages depending on the vibrationalacceleration so that for a given vibration, the movable member comes incontact with whichever of the fixed contacts that corresponds to thatparticular vibrational acceleration. Thus a single vibration sensor canproduce multistage outputs corresponding to various vibrationalacceleration values.

According to the vibration sensor disclosed in claim 3, the movablemember corresponding to a given acceleration will operate when thatacceleration is experienced, and it will come in contact with its pairedfixed contacts. Thus a single vibration sensor can produce multistageoutputs corresponding to various vibrational acceleration values.

According to the vibration sensor disclosed in claim 4, the movablegravitation element is a sphere, and the sensor can produce multistageoutputs.

According to the vibration sensor disclosed in claim 5, the samefunction of the sensor in any of claims 1-3 is achieved by the sensor ofclaim 5. In addition to being able to use the sensor, the sensor'soperating sensitivity is adjustable and multistage outputs can beproduced.

According to the vibration sensor disclosed in claim 6, the gap betweenthe contact on the movable member and the fixed contact can be adjustedby the gap adjusting means for that purpose. In addition to being ableto use the sensor, its sensitivity is adjustable and multistage outputscan be produced.

According to the vibration sensor disclosed in claim 7, the samefunction of the sensor in any of claims 1-6 is achieved by the sensor ofclaim 7. In addition, the use of snap-action switches for the switchunits minimizes any fluctuation in the operating sensitivity.

According to the vibration sensor disclosed in claim 8, a vibrationalacceleration of a given magnitude will cause the sphere to move onto theinclined surface which corresponds to that magnitude of acceleration,and this will exert pressure on the plunger to actuate one of the switchunits. Thus a single vibration sensor can produce multistage outputscorresponding to various vibrational accelerations.

According to the vibration sensor disclosed in claim 9, the movablegravitation element is a pendulum, and the sensor can produce multistageoutputs.

While the invention has been described in detail with reference to anumber of different embodiments it should be apparent to those skilledin the art that many modifications and variations are possible withoutdeparture from the scope and spirit of this invention as defined in theappended claims.

What is claimed is:
 1. A vibration sensor for sensing a vibrationalacceleration, comprising:a movable gravitation element which is movableby a vibrational acceleration; a plunger detecting a movement of saidmovable gravitation element; and a switch mechanism actuated by saidplunger, said switch mechanism comprising a plurality of switch unitseach having a different operating sensitivity.
 2. The vibration sensoraccording to claim 1, wherein each of said plurality of switch units,comprises:a movable member actuated by said plunger which is displacedby said movable gravitation element; and a plurality of fixed contactsto come into contact with said movable element, wherein the operatingsensitivity of each of said plurality of switch units is adjusted by aspatial relationship of fixed contacts with said movable member.
 3. Thevibration sensor according to claim 1, wherein each of said plurality ofswitch units, comprises:a plurality of movable members actuated by saidplunger which is displaced by said movable gravitation element; and aplurality of corresponding fixed contacts to come into contact with saidplurality of said movable elements, wherein the operating sensitivity ofeach of said plurality of switch units is adjusted by a spatialrelationship of said fixed contacts with respect to said movable member.4. The vibration sensor according to claim 1, 2, or, wherein saidmovable gravitation element is a sphere.
 5. The vibration sensoraccording to claim 1, wherein said operating sensitivity of each of saidplurality of switch units is adjusted by a means for adjusting saidspatial relationship of said fixed contacts with said movable member. 6.The vibration sensor according to claim 5, wherein said adjusting meansadjusts a gap between said fixed contacts and a movable contact on saidmovable member.
 7. The vibration sensor according to claim 1, whereinsaid switch units are snap-action type switches.
 8. The vibration sensoraccording to claim 1, wherein said movable gravitation element movesonto a plurality of inclined surfaces corresponding to said differentoperating sensitivities, when an incline component force F₂ ' ofvibration acceleration force F₂ becomes larger than an incline componentforce F₁ ' of gravitation acceleration force F₁.
 9. The vibration sensoraccording to claim 1, 2, or 3, wherein said movable gravitation elementis a pendulum.